Digital communication receivers, such as those used in Serializer/Deserializer (SerDes) high-speed communication systems, are designed to sample an analog waveform and then reliably detect the sampled data. In high-speed SerDes implementations, a lossy communication channel exists between the transmitter and the receiver, and at high data rates, the received data stream may be severely distorted, thereby requiring equalization before the received data can be effectively sampled. An effective way for equalizing channel loss and for negating the impact of intersymbol interference (ISI) is to implement a decision feedback equalizer (DFE) in the receiver.
Data encoding using encoding schemes, such as the 8b/10b encoding, wherein 8-bit words are encoded into 10-bit symbols, is commonly used in communication systems to support continuous transmission with a balanced number of ones and zeros in the data stream and to provide for the detection of single bit transmission errors. While 8b/10b encoding provides many desirable properties in a high-speed communication system, correlation between the various bits within a given 8b/10b symbol may decrease the effectiveness of the DFE of the receiver. In a DFE, each previously decided data bit of the received signal is multiplied by a DFE tap and then summed together with other DFE taps to create a correction voltage to be applied on a current sample of the received signal. During adaptation of the DFE filter, the weight values for each tap of the DFE are adapted over time using the correlation information within the receiver, with the assumption that all correlations are the result of intersymbol interference (ISI) from the channel. However, correlations between various bits of the received signal itself may lead to the determination of incorrect tap weights for the DFE, which may degrade the performance of the receiver or may result in a broken communication link between the transmitter and the receiver.
Accordingly, what is needed in the art is an improved system and method for DFE tap adaptation that reduces the effect of data correlations inherent in a data encoding scheme, such as an 8b/10b encoding scheme.